A forging press frequently has a plurality of pressing stations. A workpiece blank is loaded into the upstream pressing station, pressed, and then sequentially displaced through the downstream stations after each subsequent pressing operation. In this manner it is possible for a single forging press having three pressing stages to produce a finished workpiece with each operation, even though each workpiece must be forged three separate times.
Thus, it is known to provide a number of manipulators, holders, or tongs one less than the number of stations, and to provide mechanism capable of moving them in two orthogonal directions. Such mechanism normally simply includes a set of hydraulic cylinders connected to a carriage carrying the holders or tongs in the pressing room after the die has been lifted so that the tongs can grip the workpieces, then lift the carriage to lift the workpieces, and then displace the carriage along to the next station whereupon the workpieces are lowered and released. Finally the carriage is stepped back to its original position for carrying out of another such stepping cycle.
Such an arrangement has considerable disadvantage, the particular one being that the displacement of the tongs is relatively brusque, starting and stopping rapidly. It has been suggested to overcome this in part by means of epicyclic gearing of the type disclosed in German patent publication 2,613,269. Such an arrangement falls, far short of providing a smoothly working system with a long service life.
More particularly the known manipulators of the above-described general type have the considerable disadvantage that they have an excessive number of independently working parts. Any loss of synchronism of the parts can result in damage to the workpiece, manipulator, or press. It is also very difficult to establish just the right synchronisation between the operation of the various cylinders or motors that actuate the system.
Another disadvantage with most of the prior art systems is that the tongs remain within the press during the pressing operation. This considerably reduces the pressing area available.